Faunal Diversity in India: Annelida
This is an extract from
Annelids are true worms with a linear series of similar body segments, marked externally by intersegmental grooves and internally corresponding transverse muscular partitions (septa) extending from the body wall to the alimentary canal. A spacious body cavity, the coelom (much reduced in leeches), separates the digestive system from the outer body wall. The phylum includes thre~ classes: Polychaeta, Oligochaeta and Hirudinea. The polychaetes or bristleworms are characterized by a distinct head, bearing eyes and a number of appendages. Each segment following the 'head is lIsually furnished with a pair of lateral bristle-bearing fleshy lobes called p,lr,lpodia. Sexes are separate in most polychaetes. They are widely distributed throughout marine and estuarine environments, although there are a few freshwater species. These worms comprise both free-living and sedentary forms. The oligochaetes lack parapodia, but the bristles or setae are implanted directly in the body wall. The head is devoid of any appendages. They are hermaphrodite. On the basis of size and habitat, oligochaetes are often divided into two convenient ecological groups: Microdrili (small, mainly aquatic worms including the terrestrial family Enchytraeidae) and Megadrili (larger, mostly terrestrial forms comprising earthworms and their aquatic representatives). Hirudinea, the leeches, are devoid of setae or parapodia. They are characterized by the presence of suckers at one or both ends of the body. Like oligochaetes, they are hermaphrodite. Leeches inhabit marine, terrestrial and freshwater environments. Majority of them are blood-sucking ectoparasites and several species are free-living and predatory upon other invertebrates.
Status Of The Taxon
Global and Indian Status
The group Annelida comprises approximately 12,700 species belonging to 1,470 genera and 128 families in the world. As many as 840 species under 312 genera and 80 families, forming 6.6% of the global annelid species, occur in India. This number may substantially increase with the discovery of new taxa, especially of aquatic and enchytraeid oligochaetes, interstitial and deep-sea species.
These animals are distributed in all the ecosystems of India. Polychaetes are inhabitants of the Bay of Bengal. Arabian sea, Indian ocean and various estuaries. Sedentary polychaetes are commonly found in large number burrowing into the sea bed, forming a major part of the benthic fauna in marine habitats. They are particularly abundant in coastal areas of Andaman and Nicobar Islands, West Bengal, Orissa and Gujarat, Gulf of Mannar, Chilka and Pulicat lakes, and Hugli-Matla, Mahanadi and Godavari estuaries. They are most common between tide marks and on coral reefs and in shallow littoral waters as far as 200 fathoms.
Aquatic Oligochaete fauna is poorly known in India, and most of the species are recorded from littoral zones of small freshwater bodies like ponds, tanks, pools, ditches, etc., all over the country. Several littoral and benthic speices have been reported from a single stream, the Bagga stream at Cuddapah in Andhra Pradesh. The Enchytraeidae (pot-worms) occur in terrestrial, littoral and marine habitats, being abundant in acidic soils with high organic matter. As compared to the world fauna, only 3% of enchytraeid species have so far been reported from this region, mainly from Orissa. Earthworms are widely distributed with major areas of their concentration in tropical rain forests of northeast and peninsular India and the Ghats. Terrestrial leeches are abundant in most forests of northeast region, Darjeeling and Kumaon hills, Western Ghats and Kerala. Aquatic leeches predominate in streams and lakes throughout the country. Faunal Diversity in hldia
Biological Diversity And Its Special Features
The range of diversity amongst the Indian Annelids comprises 3 classes, 80 families, 312 genera and 840 species as mentioned earlier. Class-wise diversity is as follows: Class Polychaeta : 61 families, 200 genera and 400 species. Class Oligochaeta : 14 families, 87 genera and 381 species. Class Hirudinea : 5 families, 25 genera and 59 species.
Introduced Species diversity
Several species of earthworms have been carried in soil around roots of exotic plants from one zoogeographical realm to another. They have successfully colonized areas of introduction. As many as 49 peregrine species (13% of Indian earthworm fauna) have been introduced on the mainland. Introduced elements belong to the Acanthodrilidae (2 spp.), Criodrilidae (1 sp.), Eudrilidae (1 sp.), Glossoscolecidae (1 sp.), Lumbriidae (17 spp.), Megascolecidae (16 spp.), Ocnerodrilidae (4 spp.) and Octochaetidae (7 spp.): Peregrine European lumbricids have established in the northwest and western Himalaya with temperate-like climate because of their inherent ability to withstand cold conditions and colonize disturbed habitats due to loss of native vegetation and increase in agricultural activity. Lumbricid earthworms have also been reported from the hills of Darjeeling, Sikkirn, Arunachal Pradesh, Nilgiri, Aravali and Palni, mostly around tourist places. They form dominant components of the earthworm fauna of Himachal Pradesh and Jammu and Kashmir. Pontoscolex coretltrurus (Family Glossoscolecidae), originally from South America, is suspected to have been brought to India after 1500 A.D. and is now well established in lowlands of Kerala and Tamil Nadu. Earthworm fauna of Andaman and Nicobar Islands comprises 27 species of which 74% are exotic. Only a few endemic species of Amyntltas and Metapltire have been recorded; their relationships are probably with Indonesian earthworms. Introduced diversity in leaches is obscured, but species of Hemiclepsis, Paraclepsis and Wltitmallia appear to be exotic in this country.
Human Annelid Relationship
Man is responsible to some extent, intentionally or unintentionally, for transporting peregrine earthworms in soil around roots of plants in various parts of the country. Even some endemic species are now wide-spread due to man's interference. Biodiversity among introduced taxa has increased but declined among endemic forms, mainly due to activity of human beings.
Most of polychaete species have very wide distribution and several are cosmopolitan, obscuring their endemicity and zoogeographical relationships. About 25% of the known species from Indian waters are also found on the western shores of Europe. The pelagic forms show closer affinities with those of the Atlantic ocean.
Most Indian species of aquatic oligochaetes are also cosmopolitan. Seven species are considered truely endemic, forming 12.2% of known aquatic oligochaete fauna. Another 16 species are suspected to be endemic having close affinities with the fauna of southern hemisphere. The Enchytraeidae are represented by 21 endemic species belonging to 8 widely distributed genera. A real picture of endemicity of Indian enchytraeids could be inferred only after further exploration of these worms. Majority of earthworm species are endemic, comprising 87% of known species from the mainland and Andarnan and Nicobar Islands. The endemic elements in leech fauna constitute about 42% of known species from our country. Oosthichobdella sp. and Salifa sp. are closely allied to African species, whereas species of Dinobdella, Hirudinaria, Illebdella and Poecilobdella have affinities with southeast Asian forms. Palaearctic species are present in Kashmir and Theromyzon sexoculatllm is endemic there.
Faunal Diversity in India There are some threatened species of annelids as listed in Table 1. Table -1 List of threatened species of annelida in India A. Oligochaeta
1. Comarodrilus gravelyi Stephenson
2. Drawida nilamburensis (Bourne)
3. Detoellaetoides raoi Gates
4. Perionyx macintoshii Beddard
5. Priodoeltaeta pelluoda (Bourne)
6. Priodoscoles montanlls Gates
7. Scolioscolides bergtlreili (Michaelsen)
8. Travoscolides eocltinensis (Michaelsen)
B. Hirudinea 1. Asiatieobdella asiatica (Blanchard) -Host : Frog 2. Hirudinaria manillensis (Lesson) 3. Ozobranchus papillatlls Kaburaki-Host : Kachuga tee/llm
Polychaetes have recently gained improtance as indicator species of various degrees of marine pollution. They playa significant role in turning over sediments on the sea bottom. Some sea fishes also feed upon these organisms. Aquatic oligochaetes are important in retrieving organic matter from sediments in water bodies. They are also indicators of organic and thermal pollution. Earthworms are known to be friends of farmers. Their activities of burrowing into soil and breakdown of organic matter enhance soil fertility considerably. A large number of worms, comprising a major component to total biomass of soil invertebrates die during unfavourable season. Microbial decomposition of dead worms increases the amount of available mineralized nitrogen for growing plants. Addition of earthworms in sewage sludge and sludge-amended soils hastens in sludge decomposition. Because of their feeding habits, earthworms have been utilized for the disposal of organic wastes through vermiculture techniques for the production of organic fertilizer or the worm crop as a source of protein in fish meal and poultry feed. A peregrine African earthworm Eudrilus eugeniae and an European dung worm Eisenia fetida are being cultured on a small scale in some parts of south and west India. Potentiality of endemic Perionyx excavatus should also be explored for culture under tropical conditions. Importance of earthworms as bait in angling is well known.
Annelids are useful in medicine as valuable compounds can be extracted from their bodies for treating a variety of ailments like haemorrhoids, jaundice, rheumatism, etc. Leeches have been used as remedies for throat and inflammatory swellings in human beings on account of their property of sucking excess of blood. Anticoagulant secretion (hirudin) from the salivary glands of leeches is being experimented in research to understand the mechanism of blood dotting. These glands also contain highly specified enzymes which dissolve blood dots. Annelids are of considerable value as experimental animals because of their easy availability in all types of >ecosystems. They provide popular material for laboratory study at college/ university level.
Marine polychaetes are not seriously threatened. However, oil pollution in sea may adversely affect their populations considerably. Threats to diversity in aquatic oligochaetes, enchytraeids and leeches have not been documented. However, large scale deforestation in the northwest and western Himalaya has restricted the distribution of a land leech, Haemadipsa zeylanica agilis. However, large-scal~ deforestation, especially in the northwest and western Himalaya and parts of central India, has resulted in reduction of diversity in leech and earthworm fauna and restricted the distribution of a land leech, Haemadipsa zeylanica agilis. Indiscriminate application of pesticides and changes in agricultural practices have affected the population of earthworms. Insecticides are also responsible for changes in the distribution of aquatic oligochaetes and leeches. Host-specific parasitic leech becomes vulnerable along with decline in the population of its host.
Several endemic earthworms have restricted geographical distributions and are highly specialized for certain soil conditions. They face a serious threat from deforestation and subsequent changes; particularli deep burrowing geophagous species, which are unable to withstand altered habitats. Drawida nilamburensis, a giant earthworm, inhabits sandy soil on the bank of river Chaliar near Nilamhur in Kerala. Excavation of sand from the area has disturbed the habitat to a great extent, posing a threat to its existence. Species of Perionyx prefer soils rich in organic matter and are closely associated with different types of vegetation. Some of Perionyx sp. are at risk from deforestation, especially in Darjeeling hills, an area of their major concentration. Repeated surveys have shown a decline in the frequency of occurence of Perionyx macintoshii, another giant worm. Earthworms with very restricted distribution are vulnerable to multifarious human activities. Some of these species are : Priodoscolex montanlls and Octocltaetoides raoi (Nandi hills), Octocltaetoides kurmagarensis and Hoplochaetella kllrmagarensis (Kurmagar Island, Karwar Harbour), Priodochaeta pellilcida (Coonoor, Nilgiri hills), Dashiella khandalaensis (Western Ghats, Maharashtra) and Scolioscolides bergtheili (Darjeeling hills), and 4 species of Travoscolides (Kerala).
There are no specific past and ongoing policies and programmes for conservation of Indian Annelida. But indirect protection is being provided to freshwater oligochaetes, leeches and earthworms in existing wildlife sanctuaries, national parks, biosphere reserves and wetlands.
In view of sparce information available on the current status of vulnerable annelids, the follOWing measures are necessary as a first step: (i) to identify vulnerable annelid taxa, (li) to estimate present status of vulnerable taxa, (iii) to study the ecology and biology of threatened species and (iv) to establish habitat reserves for monotypic earthworm genera with restricted distribution.
Bah), K. N., 1950. The Indian Zoological Memoirs. I. Pheretima, 4th. edition, 84 pp. Lucknow Publishing House, Lucknow. Bhatia, M. L., 1939. On some leeches from Kashmir, Bull. Punj. Unit!. Zool., 2: 1-17. Brinkhurst, R. O. & Jamieson B. G. M., 1971. Aquatic Oligoclraetes ofthe world xii + 860 pp. University of Tronto press, Toronto and Buffalo. Chandra, M., 1983. A check-list of leeches of India. Rec. zool. SlIrlI. India, 80 : 265•290. Dash, M. c., 1983. The Biology ofEnchytraeidae (Oligoc1laeta), vii + 171 pp. International book distributors, Dehradun.
Edwards, C. A. & Lofty, J. R., 1977. Biology of Earthworms, 2nd. edition, xviii + 333 pp. Champan and Hall, London. Fauchald, K.. 1977. The Polychaete worms: Definitions and keys to the orders, Families and Genera. Nat. Hist. MilS., Los Angeles COllntry. Sci. Sr., 28 : 1-88. Fauvel, P. 1953. The fauna of India including Pakistan, Ceylon, Burma and Malay. Annelida, Polychaeta, XII 507 pp.
Gates, G. E., 1972. Burmese Earthworms. An introduction tot he systematics and biology of megadrile oligochaetes with special reference to southest Asia. Trans. Am. phil. Soc., 67 (7) : 1-326. Harding, W. A. and Moore, P. J. 1927. The Fauna of British India. Hintdinea. Taylor and Francis, London. Hartman, O. 1974. Polychaetous annelids of the Indian Ocean including an account of speices collected by members of the international Indian ocean Expeditions, 1963-64 and a catalogue and bibliography of the species from India. Pt. I. J. mar. bio., Ass. India, 16 (1) : 191-252; Pt. 2, J. mar. bioi. Ass. India, 16 (2) : 609¬ 644.
Julka, J. M. 1988. Megadrile Oligoc/laeta (Earthworms) : Haplotaxida : Lllmbricinc Megascolecoidea : Octoc/raetidae. The Fallna of India and tile adjacent cOlintries; xiv + 400 pp. Zoological Survey of India. Michaelsen, W. 1910. Oligochaeta, Das Tierreich. : 1-575. Sanjeeva Raj, P. J. 1976. Review of fish-leches of the Indian Ocean. J. mar. bioI. Ass.
India. 16 (2) : 381-397. Sims, R. W. 1980. A Classification and the distribution of earthworms of suborder Lumbricnna (Haplotaxida : Oligochaeta). BlIl1. Br. MilS. Nat. Hist. (zool), 39 (2) : 103-124. Sims, R. W. & Easton, E. G., 1972. A numerical revision of the earthworm genus P/wrelima (Megascolecidae : Oligochaeta) with the recognisation of new genera and an appendix on the earthworms collected by the Royal Society North Borneo Expedition, BioI. J. Linl!. Soc., 4 (3) : 169-268. Southern, R. 1921. Polychaeta of the Chilka Lake and also of fresh and brackish waters in other parts of India. Mem. Indian MilS., 5 : 563-659. Stephenson, J. 1923. Oligocllaeta. The Fallna ofBritish India. inclllding Ceylon and Bllrma, xxiv + 518 pp., Taylor and Francis Ltd., London. Stephenson, J. 1930. The Oligochaeta, xvi + 978 pp., Clarendon Press, London.